1. Field of the Invention
The present invention relates to a signal transmission system, and more particularly to a signal transmission system suitable for a network service in a network when subscribers increase.
2. Description of the Related Art
The extension of a portable phone service area advances rapidly at present. Also, a system for a service area transfers a subscriber data to another system for another service area so that a subscriber can receive same service regardless of service area even if the subscriber moves from the service area to the other service area. This service is called roaming service.
Because a conventional portable phone service is originally provided only in a great city, the signal between the systems is connected in PC-PC. The PC is a point code, the PC-PC means the PC of a call originating subscriber and the PC of a call receiving subscriber. The routing of a message is performed in accordance with the point code.
FIG. 1 is a block diagram illustrating a general structure of a signal transmission network. In the figure, an elliptical block shows a node of the network and a line between the nodes shows a signal transmission path. A Signaling End Point (SEP) station in the elliptical block is a portable phone station and a Signaling Transfer Point (STP) station is a switch. Also, an R-STP station is a Regional STP station and an L-STP station is a Long distance STP station.
The STP station is provided with a Message Transfer Part (MTP) and the routing for a message is carried out in accordance with the PC-PC. However, if the call receiving PC or Destination Point Code (DPC) and a Linking Group Number (LGN) route corresponding to the DPC are not registered on the MTP, it is not possible to carry out the message transmission.
For example, it is supposed that a signal is transmitted from the SEP-A station to the SEP-Z station in FIG. 1. In this case, the SEP-A station transmits a signal in which a DPC of the SEP-Z station is written, to the R-STP station 1 which accommodates the SEP-A station. If the DPC of the SEP-Z is registered on the MTP of the R-STP station 1, so that a route is recorded to reach the SEP-Z station, the signal is sent out based on the recorded route. However, if the DPC of the SEP-Z station is not registered on the MTP of the R-STP station 1, the signal can not be transmitted.
However, with the extension of the service are on the network, a new station is opened so that the number of stations increases. Thus, it has become impossible for the R-STP to manage all the PCs in the whole network. Therefore, in the conventional signal transmission system, there is a problem in that a signal can not be transmitted to an SEP whose PC is not yet registered.
In conjunction with the above description, a path managing method in an ATM-LAN is described in Japanese Laid Open Patent Application (JP-A-Heisei 7-250081). In this reference, a path management data in a path control server PCS1 is inputted and updated in advance in accordance with the structure change of the ATM-LAN. As to each of routers necessary to change the setting of new PVC and ATM switches corresponding to the routers, new routing data and connection data are acquired from the updated path management data and the routing data and connection data in the router R1 to R4 and the ATM switches SW1 and SW2 are set through communication lines Ca to C4 and C11 and C12.
Also, a network routing system is described in Japanese Laid Open Patent Application (JP-A-Heisei 8-265436). In this reference, when a passage avoiding relay station or a passage avoiding domain is written in a predetermined portion of a message, a message originating station extracts a route not to pass the passage avoiding relay station or the passage avoiding domain. Then, if there are transfer routes, the originating station determines one of the transfer routes by selecting means depending on individual routing systems to transmit to an adjacent station along the determined route. When the passage avoiding relay station or the passage avoiding domain is written in the predetermined portion of the message, a relay station extracts a route not to pass the passage avoiding relay station or the passage avoiding domain. Then, if there are transfer routes, the relay station determines one of the transfer routes by selecting means depending on the individual routing systems to transmit to an adjacent station along the determined route.
Also, an integrated radio communication method is described in Japanese Laid Open Patent Application (JP-A-Heisei 9-130405). In this reference, a radio LAN is used for communication between data terminals 3a to 3f located in a small domain and having high communication density. Also, an internet communication network 6 is used for high speed data transmission. The connection between the networks is controlled a gateway computer 1 positioned in each radio local area network. The gateway computer 1 specifies a route to a node of network and a mobile internet node which visits the node. A small size radio LAN can be configured in a home or small size office, and the gateway 10 is connected to more larger size network by the existing connection and corresponding data transmission network 8.
Also, a group management system in a network is described in Japanese Laid Open Patent Application (JP-A-Heisei 9-214540). In this reference, a terminal sends out a signal containing a transmission source address, a destination address and a type of protocol. Whether or not a destination belongs to the same group as the terminal is determined based on the type of protocol. When the terminal and the destination belong to the same group so that it is possible to communication between them, a routing process is carried out by routing processing means.
An object of the present invention is to provide a method and apparatus for signal transmission in which signal transmission is possible to an SEP in which a PC is not fully registered.
In order to achieve an aspect of the present invention, a signal transmission system includes a plurality of long distance signaling transfer point (L-STP) stations, each of which includes a plurality of regional signaling transfer point (R-STP) stations, each of which includes a plurality of signaling end point (SEP) stations. One of the plurality of SEP stations as an originating SEP station transmits a message to another of the plurality of SEP stations as a destination SEP station, the message having a header section including a point code of the destination SEP station as a DPC. One of the plurality of R-STP stations including the originating SEP station as an originating side R-STP station determines one of a route to the destination SEP station, a route to one of the plurality of R-STP stations including the destination SEP station as a destination side R-STP station, and a route to one of the plurality of L-STP stations including the destination side R-STP station as a destination side L-STP station, based on the DPC in the header section of the message, and transfers the message based on the determined route.
The originating side R-STP station may write a partial routing indicating data that the determined route is a partial route, in the header section of the message.
The originating side R-STP station preferably includes a routing data table in which full routes, partial routes and default routes are written, the full route indicating the route to the destination SEP station, the partial route indicating the route the destination side R-STP station, and the default route indicating the route to the destination side L-STP station. The originating side R-STP station refers to the routing data table based on the DPC to determine the route. In this case, the full routes are written in the routing data table for the plurality of SEP stations contained in the originating side R-STP station as a first group of SEP stations. Also, the partial routes are written in the routing data table for predetermined ones of the plurality of SEP stations as a second group of SEP stations other than the first group of SEP stations. Also the default routes are written in the routing data table for the plurality of SEP stations other than the first and second groups of SEP stations.
The originating side R-STP station writes a partial routing indicating data that the determined route is the partial route, in the header section of the message. In this case, the destination side R-STP station transfers the message to the destination SEP station based on the header section of the message including the partial routing indicating data.
Each of the plurality of SEP stations is a radio terminal.
In order to achieve another aspect of the present invention, a signal transmission method in a network including a plurality of long distance signaling transfer point (L-STP) stations, each of which includes a plurality of regional signaling transfer point (R-STP) stations, each of which includes a plurality of signaling end point (SEP) stations, includes:
transmitting from one of the plurality of SEP stations as an originating SEP station a message to another of the plurality of SEP stations as a destination SEP station, the message having a header section including a point code of the destination SEP station as a DPC;
determining a specific route by one of the plurality of R-STP stations including the originating SEP station as an originating side R-STP station, the specific route being one of a route to the destination SEP station, a route to one of the plurality of R-STP stations including the destination SEP station as a destination side R-STP station, and a route to one of the plurality of L-STP stations including the destination side R-STP station as a destination side L-STP station, based on the DPC in the header section of the message; and
transferring the message for the destination SEP station based on the determined specific route.